The present invention relates to a process for effecting the automatic manipulation of metal sheets of different dimensions by manipulator devices with exclusively mechanical holding members. The invention further relates to an automatic system for the folding of metal sheets which puts this method into practice.
It is known that the folding of metal sheets by means of folding presses is an operation which is difficult to automate both because of the complex movements to which the metal sheets must be subjected, particularly during the folding phase, and above all because of the wide variety of forms of metal sheet to be folded; if, in fact, manipulators with gripping members of mechanical type are used for metal sheets of small dimensions, for metal sheets of large dimensions, which flex during the handling if they are not adequately supported, it is necessary to employ particular tools comprising frames having a plurality of gripping points constituted by magnets or vacuum suckers; such tools, apart from the relatively high cost, are carried directly by manipulator arms and because of their bulk limit the movements of the arms themselves; moreover, such tools cannot always be utilised in that the metal sheets to be worked may not be made of ferro-magnetic materials making the magnets useless, or else have complex forms and are perforated thereby making the vacuum suckers ineffective. The main disadvantage however lies in the necessity of effecting frequent changes of the handling tools if it is necessary to work metal sheets of different dimensions on the same installation and this, which is something which cannot be effected automatically (at least not without providing a further manipulator robot for effecting the tool change, with a doubling of the installation costs) severely limits the possible increase in productivity obtainable over traditional manual handling of the metal sheets by human operators.